The present invention relates to tools adapted to recover objects lodged within a well bore. More particularly, the present invention relates to a jarring apparatus that delivers controlled percussive impact to a lodged object. In a different aspect, the present invention relates to an apparatus that provides a telemetry link to the lodged object during the jarring sequence.
During the course of drilling, completing, testing or working over a well for producing hydrocarbons, objects may become stuck within a well bore through which the hydrocarbons are recovered. Objects that can become lodged or otherwise immobile relative to a well bore can include drilling equipment, tool strings, bottomhole assemblies or other items typically conveyed into a well bore environment. In order to loosen and recover these objects, jars have been developed that have the effect of providing a jarring impact to the object.
Conventional jarring tools usually use either a mechanical or hydraulic system to loosen and dislodge a stuck object. Conventional hydraulic jars have a piston disposed in a cylinder that is filled with hydraulic oil. The piston, or jar rod, is accelerated by hydraulic fluid through a stroke. At the completion of the stroke, an impact force is delivered to the jar housing. One disadvantage of hydraulic jars involves the difficulties associated with maintaining a hydraulic fluid system in a downhole environment. These systems typically use pumps, reservoirs, fluid conduits, seals that can be expensive to incorporate into downhole tooling and can require frequent maintenance.
Mechanical jars, like hydraulic jars, typically use a piston-cylinder arrangement. The piston, however, is driven or propelled by a device such as a Bellville washer stack or other mechanical biasing mechanism. Often, the spring is compressed by pulling up on a work string until a desired spring force is reached. This spring force is then used to accelerate a piston that strikes the jar housing. Some jarring tools utilize means to reset the piston to deliver a second impact if needed. Conventional mechanical jars, however, do not satisfactorily control the delivery of the impact force nor provide a reliable arrangement to reset the jar tool.
Further, conventional jar tools are usually interposed in a string, such as a wireline or work string, that incorporates a telemetry system for communicating with one or more tools attached to the string. It is often desirable to maintain communication with these tools even when the jarring tool is activated. Conventional tool strings often use a telemetry cable that has one or more coiled portions that expand to provide added length to accommodate the extension of the jarring tool. Such devices, however, have not provided a reliable telemetry connection with the downhole tools.
The present invention addresses these and other disadvantages of conventional jarring tools.
The present invention provides an apparatus for providing a percussive or jarring force to an object having at least a portion thereof lodged in a well bore. In a preferred embodiment, the apparatus includes anvil, a hammer, and a button member. The anvil includes a sleeve and is connected to the object with a mandrel. The hammer includes an axial bore that can receive a portion of the anvil sleeve and a transverse bore in which the button member is disposed. The button member has a first position wherein the anvil sleeve cannot enter the hammer axial bore and a second position wherein the button allows the anvil sleeve to enter the hammer axial bore. The button member is actuated by a trigger that moves the button member from the first position to the second position. A spring member provided on the hammer urges the button member from the second position to the first position. Preferably, a housing encloses at least a portion of the hammer and the anvil. The housing has a first section, a second section, and a frangible member connecting the first and second sections. The frangible member is preferably a shear screw that disintegrating upon encountering a pre-determined force. Upon disintegration, the first section can move axially away from the second section. The preferred apparatus also includes a telemetry link for exchanging electrical signals with the object. In a preferred arrangement, the telemetry link includes at least one inner tube telescopically disposed within at least one outer tube. At least a portion of the inner tube and outer tube are formed of a conductive material. The inner tube is drawn out of the outer tube when the housing first section moves axially away from the housing second section.
During use, the preferred apparatus provides one or more jarring or percussive impacts to the object. An exemplary jarring sequence includes an activation phase, a loading phase, a release phase, and a reset phase. During the activation phase, an axial traction force is imposed on the tool housing to separate the two housing sections. In the loading phase, the first housing section moves axially away from the object and causes a piston to compress a biasing member. The button member, which is in the first position, prevents the hammer from sliding toward the anvil. A release phase is entered when a trigger provided on the housing first section moves the button member from the first position to the second position. Once the button member is in the second position, the biasing member accelerates the freed hammer axially against the anvil. The percussive impact of the hammer is transferred from the anvil to the object through a mandrel. If this action does not free the object, the apparatus is put into the reset phase. In this phase, the first housing section is permitted to slide axially towards the second section. This movement returns the hammer to its initial position and allows the button member to return to its first position. With the hammer and anvil interlocked by the button member, the jarring sequence can be again performed.
The axial length changes of the housing during the several phases of the jarring sequence are accommodated by the telescoping feature of the telemetry link. During separation of the housing sections, the inner tube of the telemetry link is extracted out of the outer tube. As the first housing section moves toward the second section, the inner tube slides into the outer tube. Thus, during all phases of the jarring sequence, a reliable telemetry communication path is maintained with the stuck object.
It should be understood that examples of the more important features of the invention have been summarized rather broadly in order that detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto.